<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<style>
    div{
        width: 500px;
        height: 500px;
        background-color: tomato;
        margin: 100px auto;
    }
</style>
<body>
    <div></div>
    <script>
        let div=document.querySelector('div');
        div.addEventListener('mousemove',function(e){
            let x=e.pageX-div.offsetLeft;
            let y=e.pageY-div.offsetTop;
            div.innerHTML=`x=${x},y=${y}`
        })
    </script>
</body>
</html>